From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26996 invoked by alias); 27 Apr 2011 01:40:30 -0000 Received: (qmail 26988 invoked by uid 22791); 27 Apr 2011 01:40:29 -0000 X-SWARE-Spam-Status: No, hits=-1.7 required=5.0 tests=AWL,BAYES_00,TW_CP,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mail.codesourcery.com (HELO mail.codesourcery.com) (38.113.113.100) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 27 Apr 2011 01:40:16 +0000 Received: (qmail 11993 invoked from network); 27 Apr 2011 01:40:15 -0000 Received: from unknown (HELO localhost) (froydnj@127.0.0.2) by mail.codesourcery.com with ESMTPA; 27 Apr 2011 01:40:15 -0000 Date: Wed, 27 Apr 2011 01:40:00 -0000 From: Nathan Froyd To: gdb-patches@sourceware.org Subject: [PATCH] avoid strict-aliasing warnings in gdbserver/linux-x86-low.c Message-ID: <20110427014014.GB23480@codesourcery.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit User-Agent: Mutt/1.5.17+20080114 (2008-01-14) X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2011-04/txt/msg00493.txt.bz2 I was compiling with a combined tree this evening when the build stopped with: /home/froydnj/src/combined-tree/gdb/gdbserver/linux-x86-low.c: In function ‘amd64_emit_const’: /home/froydnj/src/combined-tree/gdb/gdbserver/linux-x86-low.c:1822:3: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing] ...and several other similar errors. I don't know why, exactly; I've been compiling with a combined tree for quite some time and this is the first problem I've had. Anyway, the below patch addresses the problem by using memcpy instead, which is transformed into the same code by the compiler. Tested on x86_64-unknown-linux-gnu. OK to commit? -Nathan gdb/gdbserver/ * linux-x86-low.c (amd64_emit_const): Call memcpy instead of casting pointers. (amd64_emit_reg, amd64_emit_int_call_1, amd64_emit_void_call_2): (i386_emit_const, i386_emit_reg, i386_emit_int_call_1): (i386_emit_void_call_2): Likewise. diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c index 88f177d..027a563 100644 --- a/gdb/gdbserver/linux-x86-low.c +++ b/gdb/gdbserver/linux-x86-low.c @@ -1819,7 +1819,7 @@ amd64_emit_const (LONGEST num) i = 0; buf[i++] = 0x48; buf[i++] = 0xb8; /* mov $,%rax */ - *((LONGEST *) (&buf[i])) = num; + memcpy (&buf[i], &num, sizeof (num)); i += 8; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr; @@ -1876,7 +1876,7 @@ amd64_emit_reg (int reg) buildaddr = current_insn_ptr; i = 0; buf[i++] = 0xbe; /* mov $,%esi */ - *((int *) (&buf[i])) = reg; + memcpy (&buf[i], ®, sizeof (reg)); i += 4; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr; @@ -1959,7 +1959,7 @@ amd64_emit_int_call_1 (CORE_ADDR fn, int arg1) buildaddr = current_insn_ptr; i = 0; buf[i++] = 0xbf; /* movl $,%edi */ - *((int *) (&buf[i])) = arg1; + memcpy (&buf[i], &arg1, sizeof (arg1)); i += 4; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr; @@ -1978,7 +1978,7 @@ amd64_emit_void_call_2 (CORE_ADDR fn, int arg1) buildaddr = current_insn_ptr; i = 0; buf[i++] = 0xbf; /* movl $,%edi */ - *((int *) (&buf[i])) = arg1; + memcpy (&buf[i], &arg1, sizeof (arg1)); i += 4; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr; @@ -2301,18 +2301,19 @@ static void i386_emit_const (LONGEST num) { unsigned char buf[16]; - int i, hi; + int i, hi, lo; CORE_ADDR buildaddr = current_insn_ptr; i = 0; buf[i++] = 0xb8; /* mov $,%eax */ - *((int *) (&buf[i])) = (num & 0xffffffff); + lo = num & 0xffffffff; + memcpy (&buf[i], &lo, sizeof (lo)); i += 4; hi = ((num >> 32) & 0xffffffff); if (hi) { buf[i++] = 0xbb; /* mov $,%ebx */ - *((int *) (&buf[i])) = hi; + memcpy (&buf[i], &hi, sizeof (hi)); i += 4; } else @@ -2351,7 +2352,7 @@ i386_emit_reg (int reg) buildaddr = current_insn_ptr; i = 0; buf[i++] = 0xb8; /* mov $,%eax */ - *((int *) (&buf[i])) = reg; + memcpy (&buf[i], ®, sizeof (reg)); i += 4; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr; @@ -2451,7 +2452,7 @@ i386_emit_int_call_1 (CORE_ADDR fn, int arg1) buf[i++] = 0xc7; /* movl $,(%esp) */ buf[i++] = 0x04; buf[i++] = 0x24; - *((int *) (&buf[i])) = arg1; + memcpy (&buf[i], &arg1, sizeof (arg1)); i += 4; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr; @@ -2486,7 +2487,7 @@ i386_emit_void_call_2 (CORE_ADDR fn, int arg1) buf[i++] = 0xc7; /* movl $,(%esp) */ buf[i++] = 0x04; buf[i++] = 0x24; - *((int *) (&buf[i])) = arg1; + memcpy (&buf[i], &arg1, sizeof (arg1)); i += 4; append_insns (&buildaddr, i, buf); current_insn_ptr = buildaddr;